Marcus Treville-Layton

Marcus Treville-Layton was born Marcus Layton in 1699 and was the grandson of Henry Layton, Baron Loseley. He married Lady Isolda Treville, the eldest daughter of Elwyn Treville, 6th Marquess of Crantock. In order to prevent the title dying out since Lord Crantock had no male heirs, he petitioned the crown to allow the title to pass to his son-in-law and his descendants. The petition was granted on the condition that Marcus and Isolda changed their names to Treville-Layton which they agreed to do.

When Elwyn died, Marcus Treville-Layton inherited the Marquessate and on his death in 1764, it passed to his only son, Archibald Treville-Layton.